1. Field of the Invention
This specification relates to a magnetic switch, and more particularly, a magnetic switch, capable of preventing degradation of breaking efficiency by utilizing magnetic force (magnetism) as much as possible, in a manner of matching contact centers of a fixed core and a movable core with each other.
2. Background of the Invention
In general, a magnetic switch or a direct current (DC) relay is a type of an electric circuit switch which transfers mechanical driving force and a current signal using a principle of an electromagnet, and installed in various industrial facilities, machines, vehicles and the like.
Specifically, a relay for an electric vehicle is disposed in a battery system of an electric vehicle, such as a hybrid vehicle, a fuel cell vehicle, a golf cart and an electric forklift truck, to serve to switch on or off a flow of a main current.
FIG. 1 is a longitudinal sectional view of a magnetic switch according to the related art, and FIG. 2 is an exploded perspective view of FIG. 1.
A configuration and a fabricating process of the related art magnetic switch are described as follows. An arc chamber 2 with a fixed contact 1, a movable shaft assembly 4 with a movable contact 3, a plate 5, a fixed core 6 and a movable core 7 are sequentially laminated in a downward direction. A lower end portion of the movable shaft 8 is completely fixed to the movable core 7 in a laser-welding manner. The upper arc chamber 2 is welded onto the plate 5 by laser beams so as to fully seal a space where the fixed contact 1 and the movable contact 3 operate. Also, the fixed core 6 and the movable core 7 are covered with a cylinder 9. The cylinder 9 is then air-tightly welded onto a lower portion of the plate 5. A coil assembly 5a wound with a coil 5b and a yoke 5c are coupled to the lower portion of the plate 5.
In the magnetic switch, a magnetic path is formed along the plate 5, the yoke 5c, the movable core 7 and the fixed core 6, by a magnetic field generated in the coil 5b. In this instance, the movable core 7 is attracted to the fixed core 6 by a magnetic force generated in the fixed core 6. Responsive to this, the movable shaft 8 fixed to the movable core 7 is moved to push up the movable contact 3 coupled to an upper portion of the movable shaft 8. Accordingly, the movable contact 3 is brought into contact with the fixed contact 1 such that a current can flow therealong.
In the related art magnetic switch, the arc chamber 2 is filled therein with arc-extinguishing gas, and thus should have a sealed structure. Also, the fixed core 6 and the movable core 7 should have their centers accurately matching each other to prevent a loss of magnetic force.
Here, the cylinder 9 is fabricated by pressing, called deep drawing. However, in view of a characteristic of the pressing process, the structure of the cylinder 9 is made by pressing down a raw material. Accordingly, the material of the cylinder has a slightly inclined (tilt) angle, failing to be formed in an accurately straight form (form a right angle). This may be likely to cause interference between a lower portion of the cylinder 9 and the movable core 7. Such interference has been avoided in a manner that an outer diameter of the movable core 7 is slightly smaller than an inner diameter of the cylinder 9.
However, in this instance, abrasion due to friction between the movable core 7 and the cylinder 9 in case of a long-term use may be caused due to a gap present between the movable core 7 and the cylinder 9. That is, a problem of residual iron powders which fell from components of the movable core 7 and the cylinder 9 is caused. In addition, a failure of a uniform linear motion of the movable core is caused, which results in non-use of magnetic force to the utmost, and degradation of breaking efficiency (performance), such as an increase in a breaking time or a generation of a voltage loss.